Coloured transmission electron micrograph (TEM) of a section through demyelinated neurons (nerve cells) in a mouse model of muscular dystrophy. The myelin sheath (yellow) that insulates the nerve's axon (green) is degenerating, impairing nerve function. Muscular dystrophy is a genetic disorder typified by muscle wasting and loss of function. The muscle wasting is caused by a lack of the protein dystrophin. Research in mouse models has shown that nervous system dysfunction may also play a role in muscular dystrophies that eventually lead to problems breathing.